1. Field of the Invention
This invention relates to bronze-grey colored transparent films which are employed in glazing products. More particularly, it relates to an improved composition of such films and to a method for their production using magnetron sputtering.
2. Description of the Prior Art
A wide range of metallized films are presently commercialized for use in glazing products. These films, which can have a plastic backing, carry one or more layers of metal. The metal layers are substantially transparent but do reflect a portion of the light and/or heat falling upon them. Thus, they are used in applications such as exterior window glazings where it is desirable to hold heat in a building, hold heat out of a building, or cut down the amount of sunlight entering a building. They also can be used for their esthetic effects where they present a metallic sheen to the glazing. This sheen can be a silver chrome-like color or can be tinted grey, bronze, gold, copper, or the like.
These films can be suspended or stretched between multiple glazing panes, as shown in U.S. Pat. No. 4,335,166 issued 15 June 1982 to Lizardo, et al, or it can be directly adhered to a glass glazing material either using a glue or merely surface tension.
Representative patents relating to the general area of metallized films for glazing products include the following: U.S. Pat. No. 4,298,444, issued 3 Nov. 1981; U.S. Pat. No. 4,307,942 issued 29 Dec. 1981 to Chahrourdi; U.S. Pat. No. 4,389,452 issued 21 June 1983 to Chahrourdi, et al; U.S. Pat. No. 4,322,276 issued 30 Mar. 1982 to Meckel, et al; Japanese Patent No. 8,571,251 dated 23 Apr. 1985 of Hitachi Chemical Co. Ltd.; U.S. Pat. No. 4,497,700 issued 5 Feb. 1985 to Groth, et al; U.S. Pat. No. 4,462,883 issued 31 July 1984 to Hart; U.S. Pat. No. 4,510,190 issued 9 Apr. 1985 to Glaser; U.S. No. 4,337,990 issued 6 July 1982 to Fon, et al; U.S. Pat. No. 4,534,841 issued 13 Aug. 1985 to Anton, et al; and U.S. Pat. No. 4,022,942 issued 10 May 1977 to Grubb, et al.
Since 1985, Southwall Technologies has manufactured and sold a metallized film having an attractive bronze-grey color and a transmission over the visible spectrum of about 25 to 30%. This material has a plastic backing and employs layers of copper and a "greying" metal to impart the desired transmissivity and bronze-grey color. It is documented in the literature that copper can adversely interact with plastic substrates. This results in low adhesion of copper layers. To address this problem, our prior materials contained a primer layer of titanium. This material was laid down ostensibly as titanium metal in a sputtering process without addition of reactive gas.
While this prior product and its method of manufacture were often very acceptable, at times the product failed. These failed products have been examined and it has been observed that the failures often had the characteristics or symptoms of an improper or inadequate primer coat.
It is an object of the present invention to provide an improved bronze-grey film which is more consistent and less susceptible to failures.